1. Field of the Invention
The invention report is related to power saving in software radio receivers and mobile software radio receivers. The present invention pertains to a method for operating a software radio receiver for reducing the power consumption of software radio receivers by dynamic channel decoding based on required decoding performance and a software radio device capable of operating according to said method.
2. Description of the Related Art
The term software radio describes an implementation of a radio which may be a transceiver, receiver or transmitter or any device that has receiving or transmitting capability, in which a large proportion of the signal processing is performed and controlled by software. For example in a receiver, the antenna signal is preferably filtered, sampled and directly A/D-converted in order to make it available for digital signal processing. Typical stages that are conventionally done in the analogue domain are performed by software on a processor, like frequency conversion, mixing and/or filtering. A similar structure is applied to a transmitter or the transmitting path of a transceiver.
The present invention further pertains to the field 3G Evolution Technologies (3GET) involving Orthogonal Frequency Division Multiplexing (OFDM) transmissions. More specifically the present invention pertains to the Broadcast technology known as Digital Radio Mondiale (DRM) that may be implemented as software radio. 3.9G is the next generation for cellular networks. DRM is an emerging broadcast technology aimed as a long-term replacement of current analogue amplitude modulated (AM) radio. DRM provides huge benefits in audio quality over analogue AM radio while preserving the high transmission range typical for AM radio. DRM may also provide enhanced broadcast data services, which may not be provided by AM radio.
This capability of providing good audio quality in a long range broadcast system is based on the use of algorithms capable of repairing/compensating transmission errors. One of the known error correction algorithms is e.g. the Viterbi algorithm that is capable of providing a highly sophisticated recognition/repair capabilities. However, the Viterbi algorithm has the drawback that it requires a high amount of processing power and in turn requires a high amount of electric power consumption. Especially in the field of mobile software radio receivers, the high power consumption would significantly reduce the operation time of a battery powered mobile software radio receiver. Especially, in case of mobile software radio receivers that are used in highly varying signal quality conditions, the use of a Viterbi algorithm may significantly restrict the operation time of a mobile software radio receiver. Especially, in case of mobile software radio receivers that are used in highly varying signal quality conditions, the use of a Viterbi algorithm may be a prerequisite for enabling the operation of a mobile software radio receiver, especially in case of fading signal conditions caused by multiple reflections.
The technical background for different coding schemes may be found in “Trelliscodierung”, by J. Huber, Springer, 1992, ISBN 3-540-55792-X. Another document related to radio transmission decoding is disclosed in “A Novel Method for Convolutional Decoding Using Recurrent Neural Networks”, by Arto Rantala, VTT Electronics.
The use of DRM in mobile software radio devices is a kind of quandary: on one hand, the mobile software radio receiver requires a high processing power to compensate for varying reception or signal conditions, and on the other hand, the power consuming compensation algorithms reduce the operation time significantly so that a mobile operation is in turn restricted. The device has to be able to cope with bad signal conditions therefore the algorithms were designed for the worst case scenario, and in case of better than worst case, the algorithm performance is over specified and requires much power.